OBJECTIVES: I. Assess the antitumor activity of intravenous cidofovir in patients with Kaposi's sarcoma (KS) with and without human immunodeficiency virus (HIV) infection. II. Assess the effect of intravenous cidofovir on the load of KS-associated herpesvirus/human herpesvirus-8 in KS lesions and peripheral blood mononuclear cells by quantitative polymerase chain reaction. III. Assess the toxicity of cidofovir in KS patients with and without HIV infection. IV. Assess the effect of cidofovir on angiogenic cytokines related to the pathogenesis of KS.